Multi-speed transmission

ABSTRACT

A transmission is provided having an input member, an output member, four planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices may include clutches and brakes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/942,619 filed on Jun. 7, 2007. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The invention relates generally to a multiple speed transmission havinga plurality of planetary gear sets and a plurality of torquetransmitting devices and more particularly to a transmission havingeight or more speeds, four planetary gear sets and a plurality of torquetransmitting devices.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of frictionclutches, planetary gear arrangements and fixed interconnections toachieve a plurality of gear ratios. The number and physical arrangementof the planetary gear sets, generally, are dictated by packaging, costand desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

In an aspect of the present invention a transmission is provided havingan input member, an output member, four planetary gear sets, a pluralityof interconnecting members and a plurality of torque transmittingdevices. Each of the planetary gear sets includes first, second andthird members. The torque transmitting devices are for example clutchesand brakes. Moreover, a first interconnecting member continuouslyinterconnects the second member of the first planetary gear set with astationary member. A second interconnecting member continuouslyinterconnects the second member of the first planetary gear set with thefirst member of the second planetary gear set. A third interconnectingmember continuously interconnects the third member of the firstplanetary gear set with at least one of the second member of the secondplanetary gear set and the input member. A fourth interconnecting membercontinuously interconnects the third member of the second planetary gearset with the third member of the third planetary gear set. A fifthinterconnecting member continuously interconnects the first member ofthe third planetary gear set with the second member of the fourthplanetary gear set. Additionally, five torque transmitting devices areselectively engageable to interconnect one of the first, second, andthird members with at least one other of the first members, secondmembers, third members, and the stationary member. The five torquetransmitting devices are selectively engageable in combinations of atleast two to establish at least eight forward speed ratios and at leastone reverse speed ratio between the input member and the output member.

In another aspect of the present invention, the first of the five torquetransmitting devices is selectively engageable to interconnect the firstmember of the first planetary gear set with the third member of thefourth planetary gear set.

In still another aspect of the present invention, the second of the fivetorque transmitting devices is selectively engageable to interconnectthe second member of the second planetary gear set with the third memberof the fourth planetary gear set.

In still another aspect of the present invention, the third of the fivetorque transmitting devices is selectively engageable to interconnectthe third member of the fourth planetary gear set with the first memberof the fourth planetary gear set.

In still another aspect of the present invention, the fourth of the fivetorque transmitting devices is selectively engageable to interconnectthe third member of the fourth planetary gear set with at least one ofthe second member of the third planetary gear set and the output member.

In still another aspect of the present invention, the fifth of the fivetorque transmitting devices is selectively engageable to interconnectthe first member of the fourth planetary gear set with the stationarymember.

In still another aspect of the present invention, the third member ofthe first planetary gear set, the first member of the second planetarygear set, the third member of the third planetary gear set and firstmember of the fourth planetary gear set are sun gears, the second memberof the first, second and third planetary gear sets and the third memberof the fourth planetary gear set are carrier members and the firstmember of the first planetary gear set, third member of the secondplanetary gear set, the first member of the third planetary gear set andthe second member of the fourth planetary gear set are ring gears.

In still another aspect of the present invention, the input member iscontinuously interconnected with at least one of the third member of thefirst planetary gear set and the second member of the second planetarygear set and wherein the output member is continuously interconnectedwith the second member of the third planetary gear set.

In yet another aspect of the present invention, one of the torquetransmitting devices is a brake and four of the torque transmittingdevices are clutches.

In yet another aspect of the present invention, the stationary member isa transmission housing.

Further aspects and advantages of the present invention will becomeapparent by reference to the following description and appended drawingswherein like reference numbers refer to the same component, element orfeature.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a lever diagram of an embodiment of an eight speedtransmission according to the present invention;

FIG. 2 is a diagrammatic view of an embodiment of an eight speedtransmission according to the present invention; and

FIG. 3 is a truth table presenting the state of engagement of thevarious torque transmitting clutches in each of the available forwardand reverse speeds or gear ratios of the transmission illustrated inFIGS. 1 and 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular exampleprovided, the eight speed automatic transmission of the presentinvention has an arrangement of permanent mechanical connections betweenthe elements of the four planetary gear sets. A second component orelement of a first planetary gear set is permanently coupled to groundor a transmission housing. A first component or element of the secondplanetary gear set is permanently coupled to ground or a transmissionhousing. A third component or element of the first planetary gear set ispermanently coupled to a second component or element of the secondplanetary gear set. A third component or element of a second planetarygear set is permanently coupled to a third component or element of athird planetary gear set. Finally, a first component or element of thethird planetary gear set is permanently coupled to a second component orelement of a fourth planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10is illustrated in a lever diagram format. A lever diagram is a schematicrepresentation of the components of a mechanical device such as anautomatic transmission. Each individual lever represents a planetarygear set wherein the three basic mechanical components of the planetarygear set are each represented by a node. Therefore, a single levercontains three nodes: one for the sun gear, one for the planet gearcarrier, and one for the ring gear. The relative length between thenodes of each lever can be used to represent the ring-to-sun ratio ofeach respective gear set. These lever ratios, in turn, are used to varythe gear ratios of the transmission in order to achieve appropriateratios and ratio progression. Mechanical couplings or interconnectionsbetween the nodes of the various planetary gear sets are illustrated bythin, horizontal lines and torque transmitting devices such as clutchesand brakes are presented as interleaved fingers. If the device is abrake, one set of the fingers is grounded. Further explanation of theformat, purpose and use of lever diagrams can be found in SAE Paper810102, “The Lever Analogy: A New Tool in Transmission Analysis” byBenford and Leising which is hereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The input member 12 is coupled to the third node 14C of the firstplanetary gear set 14. The output member 22 is coupled to the secondnode 18B of the third planetary gear set 18. The second node 14B of thefirst planetary gear set 14 is coupled to a ground or transmissionhousing 50 and to the first node 16A of the second planetary gear set16. The third node 14C of the first planetary gear set 14 is coupled tothe second node 16B of the second planetary gear set 16. The third node16C of the second planetary gear set 16 is coupled to the third node 18Cof the third planetary gear set 18. The first node 18A of the thirdplanetary gear set 18 is coupled to the second node 20B of the fourthplanetary gear set 20.

A first clutch 26 selectively connects the first node 14A of the firstplanetary gear set 14 to the third node 20C of the fourth planetary gearset 20. A second clutch 28 selectively connects third node 20C of thefourth planetary gear set 20 to the second node 16B of the secondplanetary gear set 16. A third clutch 30 selectively connects third node20C of the fourth planetary gear set 20 to the first node 20A of thefourth planetary gear set 20. A fourth clutch 32 selectively connectsthe third node 20C of the fourth planetary gear set 20 to the secondnode 18B of the third planetary gear set 18. A brake 34 selectivelyconnects the first node 20A of the fourth planetary gear set 20 to theground or transmission housing 50.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofthe embodiment of the eight speed transmission 10 according to thepresent invention. In FIG. 2, the numbering from the lever diagram ofFIG. 1 is carried over. The clutches, brake and couplings arecorrespondingly presented whereas the nodes of the planetary gear setsnow appear as components of planetary gear sets such as sun gears, ringgears, planet gears and planet gear carriers.

For example, the planetary gear set 14 is a planetary gear set thatincludes a sun gear member 14C, a planet gear carrier member 14B and aring gear member 14A. The sun gear member 14C is connected for commonrotation to input shaft or member 12. The ring gear member 14A isconnected for common rotation to a first shaft or interconnecting member42. The planet gear carrier member 14B rotatably supports a set ofplanet gears 14D (only one shown) and is connected to a second shaft orinterconnecting member 44 and a third shaft or interconnecting member46. Second shaft or interconnecting member 44 is permanently connectedto ground or transmission housing 50. Each of the planet gears 14D areconfigured to intermesh with both the sun gear member 14C and the ringgear member 14A.

The input shaft or member 12 is continuously connected to an engine (notshown) or to a turbine of a torque converter (not shown). The outputshaft or member 22 is continuously connected with the final drive unitor transfer case (not shown).

The planetary gear set 16 is a planetary gear set that includes a sungear member 16A, a ring gear member 16C and a planet carrier member 16Bthat rotatably supports a set of planet gears 16D. The sun gear member16A is connected for common rotation with third shaft or interconnectingmember 46. The ring gear member 16C is connected for common rotationwith a fourth shaft or interconnecting member 48. The planet carriermember 16B is connected for common rotation with input shaft or member12 and to fifth shaft or interconnecting member 52. Each of the planetgears 16D are configured to intermesh with both sun gear member 16A andring gear member 16C.

The planetary gear set 18 is a planetary gear set that includes a sungear member 18C, a ring gear member 18A and a planet carrier member 18Bthat rotatably supports a set of planet gears 18D. The sun gear member18C is connected for common rotation with the fourth shaft orinterconnecting member 48. The ring gear member 18A is connected forcommon rotation with the sixth shaft or interconnecting member 54. Theplanet carrier member 18B is connected for common rotation with outputshaft 22. Each of the planet gears 18D are configured to intermesh withboth the sun gear member 18C and the ring gear member 18A.

The planetary gear set 20 is a planetary gear set that includes a sungear member 20A, a planet carrier member 20C that rotatably supports afirst set of planet gears 20D and a second set of planet gears 20E, anda ring gear member 20B. The sun gear member 20A is connected for commonrotation with a seventh shaft or interconnecting member 56. The planetcarrier member 20C is connected for common rotation with an eighth shaftor interconnecting member 58 and a ninth shaft or interconnecting member60. The ring gear member 20B is connected for common rotation with sixthshaft or interconnecting member 54. The first set of planet gears 20Dare configured to intermesh with both the ring gear member 20B and thesecond set of planet gears 20E. The second set of planet gears 20E areconfigured to intermesh with both the sun gear member 20A and the firstset of planet gears 20D.

The torque-transmitting mechanisms or clutches 26, 28, 30 and 32 andbrake 34 allow for selective interconnection of the shafts orinterconnecting members, members of the planetary gear sets and thehousing. For example, the first clutch 26 is selectively engageable toconnect the first shaft or interconnecting member 42 to the eighth shaftor interconnecting member 58. The second clutch 28 is selectivelyengageable to connect the fifth shaft or interconnecting member 52 toeighth shaft or interconnecting member 58. The third clutch 30 isselectively engageable to connect the seventh shaft or interconnectingmember 56 to eighth shaft or interconnecting member 58. The fourthclutch 32 is selectively engageable to connect the ninth shaft orinterconnecting member 60 to output shaft or member 22. The brake 34 isselectively engageable to connect seventh shaft or interconnectingmember 56 to ground or transmission housing 50 in order to restrict sungear member 20A from rotating relative to the ground or transmissionhousing 50.

Referring now to FIGS. 2 and 3, the operation of the embodiment of theeight speed transmission 10 will be described. It will be appreciatedthat transmission 10 is capable of transmitting torque from the inputshaft or member 12 to the output shaft or member 22 in at least eightforward speed or torque ratios and at least one reverse speed or torqueratio. Each forward and reverse speed or torque ratio is attained byengagement of one or more of the torque-transmitting mechanisms (i.e.first clutch 26, second clutch 28, third clutch 30, fourth clutch 32,and brake 34), as will be explained below. FIG. 3 is a truth tablepresenting the various combinations of torque-transmitting mechanismsthat are activated or engaged to achieve the various gear states. Actualnumerical gear ratios of the various gear states are also presentedalthough it should be appreciated that these numerical values areexemplary only and that they may be adjusted over significant ranges toaccommodate various applications and operational criteria of thetransmission 10. An example of the gear ratios that may be obtainedusing the embodiments of the present invention are also shown in FIG. 3.Of course, other gear ratios are achievable depending on the geardiameter, gear teeth count and gear configuration selected.

To establish reverse gear, the first clutch 26 and the fourth clutch 32are engaged or activated. The first clutch 26 connects the first shaftor interconnecting member 42 to the eighth shaft or interconnectingmember 58. The fourth clutch 32 connects the ninth shaft orinterconnecting member 60 to output shaft or member 22. Likewise, theeight forward ratios are achieved through different combinations ofclutch and brake engagement, as shown in FIG. 3.

It will be appreciated that the foregoing explanation of operation andgear states of the eight speed transmission 10 assumes, first of all,that all the clutches and brakes not specifically referenced in a givengear state are inactive or disengaged and, second of all, that duringgear shifts, i.e., changes of gear state, between at least adjacent gearstates, a clutch or brake engaged or activated in both gear states willremain engaged or activated.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A transmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a first interconnecting member continuouslyinterconnecting the second member of the first planetary gear set with astationary member; a second interconnecting member continuouslyinterconnecting the second member of the first planetary gear set withthe first member of the second planetary gear set; a thirdinterconnecting member continuously interconnecting the third member ofthe first planetary gear set with at least one of the second member ofthe second planetary gear set and the input member; a fourthinterconnecting member continuously interconnecting the third member ofthe second planetary gear set with the third member of the thirdplanetary gear set; a fifth interconnecting member continuouslyinterconnecting the first member of the third planetary gear set withthe second member of the fourth planetary gear set; and five torquetransmitting devices selectively engageable to interconnect one of thefirst, second, and third members with at least one other of the firstmembers, second members, third members, and the stationary member, andwherein the torque transmitting devices are selectively engageable incombinations of at least two to establish at least eight forward speedratios and at least one reverse speed ratio between the input member andthe output member.
 2. The transmission of claim 1 wherein a first of thefive torque transmitting devices is selectively engageable tointerconnect the first member of the first planetary gear set with thethird member of the fourth planetary gear set.
 3. The transmission ofclaim 2 wherein a second of the five torque transmitting devices isselectively engageable to interconnect the second member of the secondplanetary gear set with the third member of the fourth planetary gearset.
 4. The transmission of claim 3 wherein a third of the five torquetransmitting devices is selectively engageable to interconnect the thirdmember of the fourth planetary gear set with the first member of thefourth planetary gear set.
 5. The transmission of claim 4 wherein afourth of the five torque transmitting devices is selectively engageableto interconnect the third member of the fourth planetary gear set withat least one of the second member of the third planetary gear set andthe output member.
 6. The transmission of claim 5 wherein a fifth of thefive torque transmitting devices is selectively engageable tointerconnect the first member of the fourth planetary gear set with thestationary member.
 7. The transmission of claim 1 wherein the thirdmember of the first planetary gear set, the first member of the secondplanetary gear set, the third member of the third planetary gear set andfirst member of the fourth planetary gear set are sun gears, the secondmember of the first, second and third planetary gear sets and the thirdmember of the fourth planetary gear set are carrier members and thefirst member of the first planetary gear set, third member of the secondplanetary gear set, the first member of the third planetary gear set andthe second member of the fourth planetary gear set are ring gears. 8.The transmission of claim 1 wherein the input member is continuouslyinterconnected with at least one of the third member of the firstplanetary gear set and the second member of the second planetary gearset and wherein the output member is continuously interconnected withthe second member of the third planetary gear set.
 9. The transmissionof claim 1 wherein one of the torque transmitting devices is a brake andfour of the torque transmitting devices are clutches.
 10. Thetransmission of claim 1 wherein the stationary member is a transmissionhousing.
 11. A transmission comprising: an input member; an outputmember; first, second, third and fourth planetary gear sets each havingfirst, second and third members, wherein the input member iscontinuously interconnected with at least one of the third member of thefirst planetary gear set and the second member of the second planetarygear set and wherein the output member is continuously interconnectedwith the second member of the third planetary gear set; a firstinterconnecting member continuously interconnecting the second member ofthe first planetary gear set with a stationary member; a secondinterconnecting member continuously interconnecting the second member ofthe first planetary gear set with the first member of the secondplanetary gear set; a third interconnecting member continuouslyinterconnecting the third member of the first planetary gear set with atleast one of the second member of the second planetary gear set and theinput member; a fourth interconnecting member continuouslyinterconnecting the third member of the second planetary gear set withthe third member of the third planetary gear set; a fifthinterconnecting member continuously interconnecting the first member ofthe third planetary gear set with the second member of the fourthplanetary gear set; and a first torque transmitting device selectivelyengageable to interconnect the first member of the first planetary gearset with the third member of the fourth planetary gear set; a secondtorque transmitting device selectively engageable to interconnect thesecond member of the second planetary gear set with the third member ofthe fourth planetary gear set; a third torque transmitting deviceselectively engageable to interconnect the third member of the fourthplanetary gear set with the first member of the fourth planetary gearset; a fourth torque transmitting device selectively engageable tointerconnect the third member of the fourth planetary gear set with atleast one of the second member of the third planetary gear set and theoutput member; and a fifth torque transmitting device selectivelyengageable to interconnect the first member of the fourth planetary gearset with the stationary member, and wherein the torque transmittingdevices are selectively engageable in combinations of at least two toestablish at least eight forward speed ratios and at least one reversespeed ratio between the input member and the output member.
 12. Thetransmission of claim 11 wherein the third member of the first planetarygear set, the first member of the second planetary gear set, the thirdmember of the third planetary gear set and first member of the fourthplanetary gear set are sun gears, the second member of the first, secondand third planetary gear sets and the third member of the fourthplanetary gear set are carrier members and the first member of the firstplanetary gear set, third member of the second planetary gear set, thefirst member of the third planetary gear set and the second member ofthe fourth planetary gear set are ring gears.
 13. The transmission ofclaim 11 wherein the stationary member is a transmission housing.
 14. Atransmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having a sun gear, acarrier member, and a ring gear, wherein the input member iscontinuously interconnected with at least one of the sun gear of thefirst planetary gear set and the carrier member of the second planetarygear set and wherein the output member is continuously interconnectedwith the carrier member of the third planetary gear set; a firstinterconnecting member continuously interconnecting the carrier memberof the first planetary gear set with a stationary member; a secondinterconnecting member continuously interconnecting the carrier memberof the first planetary gear set with the sun gear of the secondplanetary gear set; a third interconnecting member continuouslyinterconnecting the sun gear of the first planetary gear set with atleast one of the carrier member of the second planetary gear set and theinput member; a fourth interconnecting member continuouslyinterconnecting the ring gear of the second planetary gear set with thesun gear of the third planetary gear set; a fifth interconnecting membercontinuously interconnecting the ring gear of the third planetary gearset with the ring gear of the fourth planetary gear set; and a firsttorque transmitting device selectively engageable to interconnect thering gear of the first planetary gear set with the carrier member of thefourth planetary gear set; a second torque transmitting deviceselectively engageable to interconnect the carrier member of the secondplanetary gear set with the carrier member of the fourth planetary gearset; a third torque transmitting device selectively engageable tointerconnect the carrier member of the fourth planetary gear set withthe sun gear of the fourth planetary gear set; a fourth torquetransmitting device selectively engageable to interconnect the carriermember of the fourth planetary gear set with at least one of the carriermember of the third planetary gear set and the output member; and afifth torque transmitting device selectively engageable to interconnectthe sun gear of the fourth planetary gear set with the stationarymember, wherein the torque transmitting devices are selectivelyengageable in combinations of at least two to establish at least eightforward speed ratios and at least one reverse speed ratio between theinput member and the output member.
 15. The transmission of claim 14wherein the stationary member is a transmission housing.